One of the characteristics of S-Antigen (S-Ag) and interphotoreceptor retinoid-binding protein (IRBP), which are retinal-specific antigens, is their ability, when injected in the presence of an adjuvant, to induce an intense autoimmune inflammation in the eyes of experimental animals. This disease, called experimental autoimmune uveitis (EAU), is critically dependent on T cells and antigen processing by antigen-presenting cells (APC). The first step in processing exogenous antigens is their internalization into an APC by pinocytosis or phagocytosis. Processing or breakdown of the antigen occurs within acidic endocytic vesicles, resulting in the generation of small polypeptides. Once generated, these small polypeptides must be protected from further degradation and transported to the post-Golgi complex, where they can associate with class II antigens. It is felt that heat shock proteins (hsp) may play an important role in both processes.